— II —
La communication expose ensuite sommairement les opérations pratiques de mesure
des coordonnées et les résultats obtenus par l'INSTITUT GEOGRAPHIQUE NATIONAL en
appliquant ces méthodes aux Essais Contrólés Internationaux exécutés conformément aux
recommandations de la Société Internationale de Photogrammétrie.
ANALYTICAL AEROTRIANGULATION
IN THE FRENCH GEOGRAPHIC NATIONAL INSTITUTE
(Summary of the paper to be presented to Commission III)
A - ANALYTICAL AEROTRIANGULATION
Plate-coordinates, automatically registered on the stereocomparator, are classi-
fied and corrected for distortion, earth curvature, refraction and calibrating of the coor-
dinatometers.
Relative orientation matrixes for each pair and scale transmission factors are
computed. The elements are corrected according to an internal strip adjustment, based
on height discrepancies between contiguous models. Local coordinates are then computed
in one particular system for each strip.
The principle of the adjustment method is the minimization of coordinates discre-
pancies for points belonging to different blocks. It is done separately for planimetry and
altimetry, and in a progressive way. Blocks consisting of a whole strip are first consi-
dered, then blocks consisting of a few contiguous models, and finally individual models.
The process is iterative : adjusted coordinates of all points are computed, then
position parameters of all blocks, then again adjusted coordinates, and so on ....
Residual values of the discrepancies allow the determination of systematic model
deformations. After proper correction, the iterative process is repeated, giving final
coordinates.
The program for automatic data processing, written for I. B. M. 704, may be ope-
rated in one run. There is still a possibility to stop it at various stages for checking.
Dubious points can be put aside at any of these stages.
B - INSTRUMENTAL AEROTRIANGULATION
The original data are here the x y and spatial coordinates in each model. After
corrections for earth curvature and refraction, the orientation transfer matrixes and scale
transmission factors are computed. From there on, the processing is the same as that
exposed in A.
C - Another method for analytical aerotriangulation, based on the consideration of perspec-
tive bundles of rays, is also described. Approximate values for point-coordinates and ori en-
tation parameters of bundles are necessary. They may be obtained from a preliminary com-
putation according to the method A.
The adjustment process is iterative : provisional values for point coordinates are
first computed (space intersection), then orientation parameters for each bundle (space
resection), then again point coordinates, etc...
Residual values allow the computation of systematic bundles deformations.
